Transcript Chapter 3 Section 4 PPT

States of Matter
Section 4
Section 4: Behavior of Gases
Preview
• Key Ideas
• Bellringer
• Properties of Gases
• Gas Laws
• Math Skills
States of Matter
Section 4
Key Ideas
〉What are some properties of gases?
〉How can you predict the effects of
pressure, temperature, and volume
changes on gases?
States of Matter
Section 4
Bellringer
The pressure of gas depends on how frequently the particles
of gas strike the sides of the container holding the gas. Use
your experience and, after examining each of the pairs of
drawings shown below, decide whether you think the
pressure of the contained gas has increased, decreased, or
remained unchanged. Choose the correct answer.
1. The gas in the cylinder of an automatic engine undergoes
the change shown below. Does the pressure of the gas
a. increase?
b. decrease?
c. remain unchanged?
States of Matter
Section 4
Bellringer, continued
2. The gas in the toy balloon expands outward, as
shown below. After this expansion, does the pressure of
the gas
a. increase?
b. decrease?
c. remain unchanged?
3. The temperature of the water vapor in the pressure
cooker increases. Does the pressure of the gas
a. increase?
b. decrease?
c. remain unchanged?
States of Matter
Section 4
Properties of Gases
〉What are some properties of gases?
〉Gases expand to fill their containers. They
spread out easily and mix with one another.
They have low densities and are compressible.
Unlike solids and liquids, gases are mostly
empty space. Also, gases exert pressure on their
containers.
States of Matter
Section 4
Visual Concept: Properties of Gases
States of Matter
Section 4
Gas Laws
〉How can you predict the effects of pressure,
temperature, and volume changes on gases?
〉The gas laws will help you understand and
predict the behavior of gases in specific
situations.
• gas laws: the laws that state the mathematical
relationships between the volume, temperature,
pressure, and quantity of a gas
States of Matter
Section 4
Gas Laws
• Boyle’s law relates the pressure of a
gas to its volume.
– Boyle’s law: For a fixed amount of gas at a
constant temperature, the volume of a gas
increases as the gas’s pressure
decreases. Likewise, the volume of a gas
decreases as the gas’s pressure
increases.
– P1V1 = P2V2
States of Matter
Section 4
Visual Concept: Boyle’s Law
States of Matter
Section 4
Math Skills
Boyle’s Law
The gas in a balloon has a volume of
7.5 L at 100 kPa. The balloon is released into the
atmosphere, and the gas expands to a volume of
11 L. Assuming a constant temperature, what is the
pressure on the balloon at the new volume?
1. List the given and unknown values.
Given:
V1 = 7.5 L
P1 = 100 kPa
V2 = 11 L
Unknown: P2
States of Matter
Section 4
Math Skills, continued
2. Write the equation for Boyle’s law, and rearrange the
equation to solve for P2.
P1V1 = P2V2
PV
P2  1 1
V2
3. Insert the known values into the equation,
and solve.
(100 kPa)(7.5 L)
P2 
11 L
P2 = 68 kPa
States of Matter
Section 4
Gas Laws, continued
• Gay-Lussac’s law relates gas pressure to
temperature.
– Gay-Lussac’s law: The pressure of a gas increases as the
temperature increases, if the volume of the gas does not
change. The pressure decreases as the temperature
decreases.
• Charles’s law relates temperature to volume.
– Charles’s law: For a fixed amount of gas at a constant
pressure, the volume of the gas increases as the gas’s
temperature increases. Likewise, the volume of the gas
decreases as the gas’s temperature decreases.
States of Matter
Section 4
Visual Concept: Charles’s Law